1. Field of the Invention
Embodiments of the present invention are directed to delivery of therapeutic gas to a patient and substantially simultaneously filling portable cylinders.
2. Background of the Invention
Many patients with lung and/or cardiovascular problems are required to breathe therapeutic gas in order to obtain sufficient dissolved oxygen in their blood stream. In home environments, patients may have a pressure-swing absorption (PSA) system comprising a compressor that forces atmospheric air through one or more molecular sieves. The sieve material traps nitrogen, and thus the gas exiting a molecular sieve has an increased oxygen content-oxygen-enriched gas. For this reason, PSA systems may be referred to as oxygen concentration systems and/or oxygen concentrators. While, the oxygen-enriched gas exiting a molecular sieve bed has a pressure of approximately 20 pounds per square inch (PSI), most oxygen concentrators regulate the pressure and continuously deliver therapeutic gas to the patient at approximately 5 PSI. Oxygen-enriched gas at the pressure that the gas exits the molecular sieve bed is not made available to the patient. Stated otherwise, most oxygen concentrators do not have a port from which oxygen-enriched gas at approximately 20 PSI may be supplied.
PSA systems, however, are not generally portable. So that patients may be ambulatory, therapeutic gas may be delivered from a portable cylinder. A portable cylinder, however, provides only limited volume, and therefore periodically needs to be refilled. While it is possible to have these cylinders exchanged or refilled by way of commercial home health care services, some patients have systems within their homes which perform a dual function: filling portable cylinders with oxygen-enriched gas; and providing oxygen-enriched gas to the patient for breathing. Systems such as these have come to be known as “trans-fill” systems.
Trans-fill systems need to produce oxygen-enriched gas having pressure of approximately 2700 PSI to fill a portable cylinder to a full state of approximately 2200 PSI. In order to achieve the pressure sufficient to fill a cylinder, a compressor (also known in the art as an intensifier) is used. However, 5 PSI oxygen-enriched gas may be too low an inlet pressure for an intensifier to create sufficient pressure to fill a portable cylinder. For this reason, related art trans-fill systems are integral systems, combining an oxygen concentrator with an intensifier. The intensifier is supplied oxygen-enriched gas at the pressure the gas exits the molecular sieve bed, approximately 20 PSI, and the patient is provided pressure regulated oxygen-enriched gas at approximately 5 PSI. For example, U.S. Pat. No. 5,858,062 to McCulloh et al. (assigned to Litton Systems, Inc., and thus hereinafter the “Litton patent”) discloses an integral system where oxygen-enriched gas exiting a molecular sieve bed of an oxygen concentrator is applied to a plenum. From the plenum, the oxygen-enriched gas is supplied to an intensifier, and also from the plenum the pressure of the oxygen-enriched gas is regulated and supplied to a patient port. Likewise, U.S. Pat. No. 5,988,165 to Richey, II et al. discloses an integral system where, much like the Litton patent, oxygen-enriched gas exiting a molecular sieve bed of an oxygen concentrator is provided to a compressor, and regulated to 5 PSI before being provided to the patient.
Thus, what is needed is a trans-fill method and system that is not constrained to having an integral oxygen concentrator, and thus could use oxygen-enriched gas provided from any third party oxygen concentration system or other source of oxygen-enriched gas.